Methyltrichlorosilane: Difference between revisions
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| Appearance = colorless liquid |
| Appearance = colorless liquid |
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| Density = 1.273 g cm<sup>−3</sup> |
| Density = 1.273 g cm<sup>−3</sup> |
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| MeltingPt = -77 |
| MeltingPt = -77 °C |
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| BoilingPt = 66 |
| BoilingPt = 66 °C |
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| Solubility = reaction in water |
| Solubility = reaction in water |
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| SolubleOther = soluble in [[methylene chloride]]}} |
| SolubleOther = soluble in [[methylene chloride]]}} |
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:MeSi(OH)<sub>3</sub> → MeSiO<sub>1.5</sub> + 1.5 H<sub>2</sub>O |
:MeSi(OH)<sub>3</sub> → MeSiO<sub>1.5</sub> + 1.5 H<sub>2</sub>O |
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The [[silanol]] is unstable and will eventually condense to give a polymer network and water. Thus, compounds like methyltrichlorosilane are precursors to various organo-[[siloxane]] polymers. This reaction is particularly important because silicon-alkyl bonds are thermally stable and resistant to oxidation.<ref name = chemistry>Rochow, E. "An Introduction to the Chemistry of the Silicones." New York: John Wiley & Sons, Inc., 1946. ISBN |
The [[silanol]] is unstable and will eventually condense to give a polymer network and water. Thus, compounds like methyltrichlorosilane are precursors to various organo-[[siloxane]] polymers. This reaction is particularly important because silicon-alkyl bonds are thermally stable and resistant to oxidation.<ref name = chemistry>Rochow, E. "An Introduction to the Chemistry of the Silicones." New York: John Wiley & Sons, Inc., 1946. ISBN 1443722863</ref> Methyltrichlorosilane can be used as a means of cross-linking polymers to give a three-dimensional network. |
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Because of the rigid nature of the polymers that methyltrichlorosilane can form, MeSiCl<sub>3</sub> has many industrial applications. For instance, methyltrichlorosilane vapor reacts with water on surfaces to give a thin layer of methylpolysiloxane, which changes the contact angle of the surface to water. This effect arises because of the oriented layer of methyl groups, making a water-repellent film.<ref name = chemistry/> Filter paper treated with methyltrichlorosilane allows organic solvents to pass through, but not water. Another benefit of such water-repellent films is that the polymers formed are stable: one of the only ways to remove the [[siloxane]] film is by acid strong enough to dissolve silicone.<ref name = chemistry/> |
Because of the rigid nature of the polymers that methyltrichlorosilane can form, MeSiCl<sub>3</sub> has many industrial applications. For instance, methyltrichlorosilane vapor reacts with water on surfaces to give a thin layer of methylpolysiloxane, which changes the contact angle of the surface to water. This effect arises because of the oriented layer of methyl groups, making a water-repellent film.<ref name = chemistry/> Filter paper treated with methyltrichlorosilane allows organic solvents to pass through, but not water. Another benefit of such water-repellent films is that the polymers formed are stable: one of the only ways to remove the [[siloxane]] film is by acid strong enough to dissolve silicone.<ref name = chemistry/> |
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{{reflist}} |
{{reflist}} |
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{{commons category|methyltrichlorosilane}} |
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[[Category:Silanes]] |
[[Category:Silanes]] |
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Revision as of 10:24, 27 December 2011
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| Names | |||
|---|---|---|---|
| IUPAC name
Trichloromethylsilane
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| Other names
Methyltrichlorosilane
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| Identifiers | |||
| ECHA InfoCard | 100.000.821 | ||
CompTox Dashboard (EPA)
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| Properties | |||
| CH3Cl3Si | |||
| Molar mass | 149.47 g·mol−1 | ||
| Appearance | colorless liquid | ||
| Density | 1.273 g cm−3 | ||
| Melting point | -77 °C | ||
| Boiling point | 66 °C | ||
| reaction in water | |||
| Solubility | soluble in methylene chloride | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Methyltrichlorosilane, also known as trichloromethylsilane, is an organosilicon compound with the formula CH3SiCl3. At room temperature, it is a colorless liquid with a sharp odor similar to that of hydrochloric acid. As methyltrichlorosilane is a reactive compound, it is mainly used a precursor for forming various cross-linked siloxane polymers.
Preparation
Methyltrichlorosilane results from the “direct reaction” of chloromethane with elemental silicon in the presence of a copper catalyst, usually at a temperature of at least 250 °C.[1]
- 3 CH3Cl + Si → CH3SiCl3 + C2H4 + H2
While this reaction is currently the standard in industrial silicone production and is nearly identical to the first direct synthesis of methyltrichlorosilane, the overall process is inefficient with respect to methyltrichlorosilane.[2] Even though dimethyldichlorosilane is usually the major product, if methyltrichlorosilane is needed, the amount of metal catalyst is reduced.[1]
Reactions and Applications
Reagent in Organic Synthesis
A combination of methyltrichlorosilane and sodium iodide can be used to cleave a variety of carbon-oxygen bonds such as methyl ethers.
- R'OR + MeSiCl3 + NaI + H2O → R'OH + RI + MeSiCl2(OH) + NaCl
Esters and lactones can also be cleaved with methyltrichlorosilane and sodium iodide to give the corresponding carboxylic acids. Acetals convert to carbonyl compounds. Thus, methyltrichlorosilane can be used to remove acetal protecting groups from carbonyl compounds under mild conditions.[3]
- RR'C(OMe)2 + MeSiCl3 + NaI → RR'CO + 2 MeI + MeSiCl2(OMe) + NaCl
Finally, methyltrichlorosilane and sodium iodide can be used as a means of converting alcohols to their corresponding iodides; however, this reaction does not work as well with primary alcohols.[3]
- ROH + MeSiCl3 + NaI → RI + MeSiCl2(OH) + NaCl
Silynes
Methyltrichlorosilane is mainly used to form polymers such as poly(methylsilyne).
- n MeSiCl3 + 3n Na →[MeSi]n + 3n NaCl
Poly(methylsilyne) is soluble in organic solvents, and can be applied to surfaces before being pyrolyzed to give the ceramic material, silicon carbide.[4] Poly(methylsilyne) can be formed into various shapes before being pyrolyzed.
Silicones
The most common reaction of methyltrichlorosilane is its hydrolysis:
- MeSiCl3 + 3 H2O → MeSi(OH)3 + 3 HCl
- MeSi(OH)3 → MeSiO1.5 + 1.5 H2O
The silanol is unstable and will eventually condense to give a polymer network and water. Thus, compounds like methyltrichlorosilane are precursors to various organo-siloxane polymers. This reaction is particularly important because silicon-alkyl bonds are thermally stable and resistant to oxidation.[5] Methyltrichlorosilane can be used as a means of cross-linking polymers to give a three-dimensional network.
Because of the rigid nature of the polymers that methyltrichlorosilane can form, MeSiCl3 has many industrial applications. For instance, methyltrichlorosilane vapor reacts with water on surfaces to give a thin layer of methylpolysiloxane, which changes the contact angle of the surface to water. This effect arises because of the oriented layer of methyl groups, making a water-repellent film.[5] Filter paper treated with methyltrichlorosilane allows organic solvents to pass through, but not water. Another benefit of such water-repellent films is that the polymers formed are stable: one of the only ways to remove the siloxane film is by acid strong enough to dissolve silicone.[5]
Another use for methyltrichlorosilane is in the production of methyl silicone resins. Because of the stability of the cross-linked polymers that form after condensation, the resin can be heated to 550 °C in a vacuum without decomposition, making it an ideal material for electrical insulation at high temperatures.[5] Thus, these resins can be used to coat computer chips or other electronic parts since they both repel water and provide thermal isolation.
References
- ^ a b Rösch, L; et al. “Silicon Compounds, Organic.” Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim, 2005. DOI: 10.1002/14356007.a24_021
- ^ Rochow, E. The Direct Synthesis of Organosilicon Compounds. J. Am. Chem. Soc. 1945, 67, 963. DOI: 10.1021/ja01222a026
- ^ a b Olah, G; et al. “Methyltrichlorosilane.” Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons, Inc., 2001. DOI: 10.1002/047084289X.rm265
- ^ Bianconi, Patricia A.; Pitcher, Michael W.; Joray, Scott. “A method of preparing poly(methyl- or ethyl-silyne) and silicon carbide ceramics therefrom.” U.S. (2006), 15 pp. CODEN: USXXAM US 6989428 B1 20060124 CAN 144:129423 AN 2006:65860.
- ^ a b c d Rochow, E. "An Introduction to the Chemistry of the Silicones." New York: John Wiley & Sons, Inc., 1946. ISBN 1443722863
